Weight loss and machine settings
Average weight loss, cumulative (%)
RH profiles of linear and non-linear weight loss including a fine tuning program 12
80
10
Setpoint RH
70 60
linear fine tuning
50 40
non-linear
30 0 2 4 6 8 10 12 14 16 18 Incubation time (days)
linear
8 6 4
fine tuning
2
non-linear
0 0 2 4 6 8 10 12 14 16 18 Incubation time (days)
ec
te
d
The amount of moisture in the ambient air of the egg in the incubator determines the pattern of weight loss. Assess chick quality and the hatchability rate in combination with weight loss. Based on this, you can make minor adjustments using the ventilation and/or relative humidity setpoint. The various stategies have an effect on the weight loss over time.
pr ot
Opening the door disrupts the climate The RH in the incubator is approx. 55% and the machine temperature is 38°C for the first days. Assume the air outside the incubator has a temperature of 20°C with an RH of 55%. If you open the door, 50% of the air is replaced. This causes the temperature in the incubator to drop to 29°C and the RH rises to 62%. You close the door and the temperature has to increase again. As a result, the RH drops to 37% very quickly. These are immense climate fluctuations! So, it is essential to avoid opening the door of the incubator in the first few days. Pay attention to doors that do not close or seal properly! The climate fluctuations this causes will reduce the uniformity and increase the spread in the hatch window. During the first few days, the embryos are particularly sensitive to temperature fluctuations, and less to variations in humidity. But opening the door will disrupt the uniform embryo temperature, especially if sprayers are then activated to restore the RH.
co
py
rig
ht
The egg must evaporate and lose moisture (= weight) in the setter. An average egg loses about 10-12% moisture in the first 18 days of the incubation process. For an egg that weighs 60 g this translates to a total 6-7 g weight loss, or 0.6-0.7% per day with a linear moisture loss profile (constant conditions of 37.8°C/100°F machine temperature and 55% RH). You can also opt for a non-linear moisture loss profile. If the air inlets are kept closed for the first few days, you must then use more ventilation to remove the moisture and lower the RH later in the process. Ventilation also removes CO2. The risk of a too extreme/excessive non-linear moisture profile is that the embryo will dehydrate during the final days (day 17/18) of the setting phase. There is also a risk of introducing too much cold air which will create cold spots. If too much moisture is extracted by excessive ventilation, humidification is often required from day 12 to prevent dehydration. However, the general advice is: no humidifiers in the setter! Bacteria can only multiply with water. Removing moisture through ventilation to manage how much moisture is lost is necessary for: • Optimal (natural) weight loss of the egg. • Optimal mineral balance in the embryonic parts. • Optimal chick quality. There are apps that can calculate the water content of the air based on temperature and relative humidity. You can also use the Mollier diagram to calculate this.
Outside
CALCULATION EXAMPLE Required ventilation to remove moisture A batch of 57,600 eggs loses a total of 0.8 to 1.0 litres of moisture per hour. Depending on the properties of the inlet air and exhaust air, you can calculate the required ventilation volume per hour. Inlet air of 25°C with 50% RH contains 11.5 g/m3 of moisture. Exhaust air of 37°C and 55% RH contains 24.1 g/m3 moisture. The difference is 12.6 g water (moisture). To remove 0.8-1.0 kg, ventilation (VH2O) of 63-79 m3/h (800/12.6 to 1,000/12.6) is required.
3. P r in c i p l e s o f a r t i f i c i al i n cu bati o n
1. Incubator closed.
2. Incubator opened.
3. Incubator closed again.
37
